Some problems of nonequilibrium copolycondensation

The influence of the reactivity of the starting compounds and reaction conditions on the formation of the macromolecules of copolymers has been investigated for a nonequilibrium copolycondensation in solution by acceptor-catalytic polyesterification. In the nonequilibrium copolycondensation in solution, copolymers with different distributions of units may be formed, depending on various factors. Introduction of all amounts of acid chloride (intermonomer) in the beginning of the nonequilibrium copolycondensation leads to the formation of copolymers with statistical distribution of the units independent of the difference in reactivity of the comonomers used. For synthesis of copolymers with a block structure by one-stage nonequilibrium polycondensation in solution the initial comonomers must have different reactivities (r ≠ 1) and the rate of intermonomer introduction must be lower than that of its reaction with the more reactive comonomer. On varying the above factors, block copolymers with different lengths of block segments may be obtained.     

Reaction kinetics in dilute solutions of chain molecules carrying randomly spaced reactive and catalytic chain substituents. II. Dependence of the ring closure probability on the solvent medium and the nature of the chain backbone

Ternary copolymers of acrylamide or methacrylamide with small proportions of comonomers carrying reactive p-nitrophenyl ester and catalytic pyridine groups in the side chains were prepared. The kinetics of the ester solvolysis was followed in highly dilute solutions, so that the rate was controlled by interaction of groups carried by the same chain backbone. Data were obtained in water and aqueous methanol and were interpreted by a computer simulation procedure in terms of the dependence of the probability of encounter between two chain substituents on their spacing along the chain backbone. This probability decreased more slowly with increasing separation of the interacting groups when the solvation of the polymer was reduced, but even in solvents approaching θ conditions the results deviated from theoretical predictions for chains without excluded volume. The formation of cyclic conformations is considerably more difficult in methacrylic than in acrylic chains, although the chain flexibility, as characterized by unperturbed chain dimensions, is very similar in the two systems.     

Symmetric Versus Asymmetric “Homologous” Vinylic Cross‐Linkers in Two‐Components Networks: Formation of Pseudo‐Conetworks or Pseudo‐IPNs

Radical copolymerizations of heterologous comonomers are compositionally heterogeneous, unless the reaction is performed in continuous conditions. A bicomponent network prepared from a heterogeneous reaction like the mentioned before is therefore a complex structure where chains with different compositions are linked through the cross‐linker molecules. It is theoretically shown here that the use of cross‐linkers with different structural homologies toward the two comonomers may lead to very different topologies. Thus, a mixture of symmetric cross‐linkers, each one homologous to each comonomer, tends to form interpenetrated networks (IPNs). However, the use of a single bihomologous asymmetric cross‐linker, where each of the functionalities is homologous toward each of the comonomers, tends to form conetworks. It is shown here that the higher the differential reactivity between the groups, the higher is the tendency toward these extreme structures.

     

Structural defects in poly(vinyl chloride)—V. Thermal and photodegradation of copolymers of vinyl chloride with various acetylene derivatives

Vinyl chloride has been copolymerized with various acetylene derivatives in bulk at 50. It has been shown by ozonolysis that these copolymers contain a significantly increased amount of internal double bonds. A comparison of the thermal and photodegradation behaviours of the copolymers has been made. The built-in double bonds show an effect on the reactivity of the adjacent allylic chlorine depending on the electron-withdrawing or repelling nature of the substituent. Among the comonomers investigated, copolymers containing 3-chloropropine have the least reactive defect sites, because of the electron-withdrawing chloromethyl substituent. On the contrary, the electron-repelling n-butyl group, built-in by using hexine-1 as comonomer, results in enhanced reactivity of the allylic chlorines.     

Regularities of diene copolymerization by coordination catalytic systems and the mechanism of stereoregulation

A study has been conducted of the relative reactivity of a series of dienes (butadiene, isoprene, 2,3-dimethylbutadiene, cyclohexadiene-1,3), as well as of butadiene and styrene, in copolymerization by various coordination catalyst systems based on transition metals: nickel, cobalt, titanium, chromium, molybdenum, and tungsten. The microstructure of homopolymers and copolymers of dienes has been investigated. Regularities have been established in the mutual influence of the comonomers on the microstructure of a polymer chain. Experimental data on the influence of the concentration of diene monomer, and electron-donating and electron-accepting compounds on the microstructure of polydiene chain have been used in discussing the alternative mechanisms of stereoregulation in diene polymerization by active centers of the π-allyl type.     

Reactive processing of polymers: Effect of bifunctional and tri-functional comonomers on melt grafting of glycidyl methacrylate onto polypropylene

Two reactive comonomers, divinyl benzene (DVB) and trimethylolpropane triacrylate (TRIS), were evaluated for their role in effecting the melt free radical grafting reaction of the monomer glycidyl methacrylate (GMA) onto polypropylene (PP). The characteristics of the GMA-grafting systems in the presence and absence of DVB or TRIS were examined and compared in terms of the yield of the grafting reaction and the extent of the main side reactions, namely homopolymerisation of GMA (poly-GMA) and polymer degradation, using different chemical compositions of the reactive systems and processing conditions. In the absence of the comonomers, i.e. in a conventional system, high initiator concentrations of peroxides were typically required to achieve the highest possible GMA grafting levels which were found to be generally low. Concomitantly, both poly-GMA and degradation of the polymer by chain scission takes place with increasing initiator amounts. On the other hand, the presence of a small amount of the comonomers, DVB or Tris, in the GMA-grafting system, was shown to bring about a significant increase in the grafting level paralleled by a large reduction in poly-GMA and PP degradation. In the presence of these highly reactive comonomers, the optimum grafting system requires a much lower concentration of the peroxide initiator and, consequently, would lead to the much lower degree of polymer degradation observed in these systems. The differences in the effects of the presence of DVB and that of TRIS in the grafting systems on the rate of the GMA-grafting and homopolymerisation reactions, and the extent of PP degradation (through melt flow changes), were compared and contrasted with a conventional GMA-grafting system.     

Acrylonitrile Copolymerizations. VI. Influence of the Comonomer on the Intramolecular Cyclization Reaction

The intramolecular cyclization reaction involving the polymerization of cyano groups reported in a previous paper for the system acrylonitrile-vinyl chloride is studied for other comonomers with acrylonitrile including vinyl acetate, vinylidene chloride, butadiene, styrene, methyl acrylate, and methyl methacrylate. It is shown that the extent of the reaction is governed by the reactivity of the comonomer-unit ended radical, but the cyclization reaction cannot explain all the kinetic deviations observed.     

Et(Ind)_2ZrCl_2/MAO催化乙烯和ω-对甲苯基-α-烯烃共聚合的研究

使用Et(Ind)2ZrCl2/MAO催化剂催化乙烯和3种ω-对甲苯基-α-烯烃(对甲苯基-1-丙烯,4-对甲苯基-1-丁烯,6-对甲苯基-1-己烯)共聚,主要研究了共单体加入量对催化剂活性和所得共聚物性能的影响.4-对甲苯基-1-丁烯表现出最好的共聚性能.使用1H-NMR、13C-NMR、GPC和DSC对共聚物进行了表征.     

Polymerization and copolymerization of an isocyanate blocking agent. N-(1,1′-dimethyl-3-oxobutyl) acrylamide oxime. Mechanical and thermal properties

The bulk polymerization and copolymerization of N-(1,1′-dimethyl-3-oxobutyl) acrylamide oxime have been studied. Polymerization of diacetone acrylamide oxime was carried out with different initiating systems. The rate of polymerization of diacetone acrylamide oxime with azoisobutyronitrile as the initiating system was much higher than with peroxides. However, in the case of perester initiating systems (t-butyl perbenzoate and t-butyl per ethyl-2-hexanoate), cobalt salt promoted the polymerization rate markedly. Diacetone acrylamide oxime readily formed copolymers with a variety of comonomers (crosslinking agents and reactive diluents). Gel permeation chromatography has shown a higher reactivity of diacetone acrylamide oxime with trimethylol propane trimethacrylate as crosslinking agent and N-vinyl-pyrrolidone as reactive diluent. Therefore, the dynamic mechanical analyses presented an increase in T_g with trimethylolpropane trimethacrylate and N-vinyl-pyrrolidone as comonomers. The terpolymer formed with diacetone acrylamide oxime, trinethylolpropane trimethacrylate, and N-vinyl-pyrrolidone exhibited interesting mechanical properties and high temperature behavior.     

Thermodynamics of homogeneous equilibrium copolymerization from the point of view of the Flory-Huggins theory

A general treatment of the thermodynamics of binary copolymerization from the point of view of the Flory-Huggins theory is given. The relations allow one to determine, on the basis of experimental data, the thermodynamic parameters of copolymerization and the parameters of intercomponent interaction (χ). On the other hand, when these parameters are known, it is possible to predict, for any initial set of conditions, the equilibrium concentrations of comonomers and the equilibrium microstructure of a copolymer. The presented simulations indicate that positive values of interaction parameters increase the volume fractions of copolymer units in equilibrium with comonomers, in comparison to an analogous copolymerization system without intercomponent interactions.     

Copolymerization of propylene with 1-butene and 1-pentene with the isospecific catalytic system rac-Me2Si(4-Ph-2-MeInd)2ZrCl2-MAO

The copolymerization of propylene with 1-butene and 1-pentene at 60°C in the propylene bulk in the presence of the homogeneous isospecific metallocene catalyst of the C₂ symmetry rac-Me₂Si(4-Ph-2-MeInd)₂ZrCl₂ activated by polymethylaluminoxane is studied. Copolymers containing up to 30 mol % 1-butene and up to 10 mol % 1-pentene are synthesized. For the copolymerization of the above monomers, reactivity ratios are estimated to be equal to unity, thereby indicating the azeotropic character of the process. It is found that the distribution of comonomer units in the copolymers is close to statistical. For both comonomers, the comonomer effect is observed: an increase in the rate of propylene polymerization after addition of a small amount of a less reactive comonomer. The addition of 1-butene and 1-pentene to polypropylene shows a weak effect on the stereoregularity of chains but causes a marked reduction in the molecular mass of the polymer and changes its thermophysical characteristics and mechanical properties. An X-ray diffraction study of the copolymers is performed.     

Emulsion polymerization. VI. Concentration of monomers in latex particles

Nonpolymerizing latex particles surrounded by an aqueous phase saturated with monomer absorb only a finite amount of monomer, even if the monomer is a good solvent for the polymer, because the surface energy of each particle increases on swelling. At equilibrium the change in surface energy and the free energy of mixing exactly balance. Equations based on this thermodynamic principle predict with good accuracy the saturation swelling of crosslinked and uncrosslinked latex particles and the partitioning of monomer between the aqueous phase and latex particles at partial saturation. The available experimental data on swelling of latex polymers with monomers are reviewed. Earlier papers assumed that during emulsion polymerization the monomer concentration in the latex particles is independent of conversion as long as monomer droplets are present. This assumption is shown to be a justifiable approximation. The thermodynamics of the swelling of latex particles with a blend of two monomers is presented. The calculations indicate that copolymerization in emulsion should define reactivity ratios differing from those of homogeneous copolymerization by not more than 40% if the solubility of the comonomers in water is low. The reactivity ratio scheme is strictly applicable to emulsion copolymerization if the solvent properties of the two comonomers are identical.     

Controlled Activity Polymers. IV. Copolymers of 2-(1-Naphthylacetyl)Ethyl Acrylate With Hydrophilic Comonomers: Synthesis and Characterization

2-(1-Naphthylacetyl)ethyl acrylate (NAEA) was synthesized by esterification of 1-naphthylacetic acid (NAA) and 2-hydroxyethyl acrylate (HEA) and then polymerized to obtain the polymer-bound auxin NAA. The resulting polymer is potentially useful as a plant growth regulator through hydrolytic release of NAA. Copolymers of NAEA with hydrophilic comonomers were prepared by solution polymerization. The copolymer compositions were determined from elemental analysis, ¹³C-NMR, and UV spectroscopy. The copolymer microstructure was predicted from the reactivity ratios in order to investigate the influence on the behavior of controlled release. These model structures will be utilized for assessment of structure/hydrolysis relationships in a subsequent paper.     

Biodegradable polycarbonates containing side carboxyl groups—synthesis,properties, and degradation study

The main objective of the presented research was to synthesise biodegradable aliphatic polycarbonates containing reactive carboxyl pendant groups and to examine the influence of the copolymer chain microstructure and composition on the process of their hydrolytic degradation and cytocompatibility. The work describes copolymerization of cyclic trimethylene carbonate derivative containing benzyl‐ester pendant group (benzyl 5‐methyl‐2‐oxo‐1,3‐dioxane‐5‐carboxylate) with trimethylene carbonate. The copolymerization was conducted with the use of zinc (II) and lanthanum (III) acetylacetonates as ring‐opening polymerization coordination initiators. Detailed NMR analysis allowed to define the microstructure of the obtained copolymers, which depended on the composition and type of used initiator. The final tapered chain microstructure of the obtained copolymers was related to huge differences in comonomers reactivity and evidenced low level of transesterification of the main copolymer backbone. Chosen copolymers, with unprotected carbonyl groups, were subjected to in vitro degradation test and cytocompatibility studies. It was found that high concentration of carboxyl groups resulted in copolymers which formed hydrogels and were very prone to hydrolytic degradation; they were also cytotoxic toward osteoblast‐like MG 63 cells. Copolymers with lower content of carboxyl groups were found less susceptible to degradation and cytocompatible with studied cells. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2756–2769     

Thermodynamics of water interaction with 5-vinyltetrazole copolymers with different hydrophilic-hydrophobic balances

The thermodynamics of interaction with water and the behavior of 5-vinyltetrazole copolymers with comonomers of different chemical natures and hydrophilicities in aqueous media have been studied. It has been shown that the presence of side perfluoroalkyl and disubstituted tetrazole fragments, which ensure a strong self-association of polymer chains in copolymer macromolecules, favors a greater decrease in water affinity of polymers compared to the effect of hydrophobic alkyl substituents.     

Radiation-induced copolymerization of trioxane: Reactivities of some cyclic ether comonomers

Copolymerization of trioxane solid state induced by gamma radiation with oxycyclic comonomers such as penta acetyl glucose, tetrahydrofuran, styrene oxide, and 1,3 dioxolane has been reported. The relative yields, properties of the copolymers, and the reactivities of the comonomers are discussed. A mechanism for the reactivity is presented.     

STUDY ON SOLID STATE POLYCONDENSATION OF POLYETHYLENE TEREPHTHALATE COPOLYMERS

The kinetic data of solid state polycondensation of PET and its copolymers are determined.It is shown that the reaction rate of copolycondensation is higher than that of PET polyconden-sation, and increases with the comonomers content. But the reaction rate of copolycondensationin melt state of this kind of copolymers is lower than that of PET. It is considered that the chemi-cal reactivity of comonomer is the main factor which affect the polycondensation in melt state,whereas the aggregative structure of the polymer is the main factor in solid state. The crystallinity and crystallite size of the copolymers have been measured by X-ray method.     

Mesoscopic simulation of the synthesis of enzyme-like catalysts

A model based on the mesoscale simulation technique was developed for predicting the conditions for artificial enzyme formation from N-vinylcaprolactam (VCL) and N-vinylimidazole (NVI) by radical copolymerization of pre-synthesized poly-VCL blocks of different molecular weight with VCL and NVI comonomers. This synthetic procedure gives model copolymer chains. Upon a change in the solvent nature, these chains are able to form compact two-layer globular nanostructures with core–shell type morphology if the fraction of the first poly-VCL block is 25–38% of the total copolymer and the fraction of NVI monomers in the reaction mixture (in the concentration range considered) is maximum.     

Kinetics of the Fischer-tropsch reaction

Long carbon chains: Self-assembly of monomeric carbon intermediates into long-chain hydrocarbons on catalytically reactive surface was studied when full reversibility of the chain growth is included in the kinetic model. Using Br?nsted-Evans-Polanyi relations, the maximum chain growth as a function of the surface reactivity is predicted.     

Polyester oligodiols by cationic AM copolymerization of L,L‐lactide and ε‐caprolactone initiated by diols

Cationic copolymerization of L,L ‐lactide (LA) and ε‐caprolactone (CL) initiated by low molecular weight diols in the presence of acid catalyst gives corresponding copolyesters terminated at both ends with hydroxyl groups in practically quantitative yield. Copolymerization proceeds by Activated Monomer mechanism. LA is consumed preferentially and at the later stages of copolymerization the reaction mixture is enriched with CL. In spite of that, random distribution of both units is observed and end‐groups are mainly ? LA‐OH groups and not ? CL‐OH groups. This is explained by the fact that to reach high conversion of both comonomers the relatively long reaction times are required and at those conditions transesterification reaction becomes significant. Thus the microstructure of copolymers and the nature of the end‐groups is governed by transesterification rather then by the kinetics of comonomers incorporation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3090–3097, 2007